Rheostat.



l No. 687,044. Patented Nov. I9, |901.

F. MACKINTGSH.

RHEOSTAT.

(Application filed Apr. 22, 1901.)

(lo Model.)

Witnesses. Inventor.

K FrederickMackintosh Z )OSM/Qd,

UNITED YSTnTEs PATENT OEEICE.

FREDERICK MACKINTOSH, OE SCHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEIV YORK.

RH EOSTAT.

SPECIFICATION' forming part of Letters PatentNo. 687,044, dated November 19, 1901.

Application filed April 22, 1901.

.To @ZZ wwne t may concern,.-

Beit known that I, FREDERICK MncKN- TosH, a citizen of the United States, residing at Schenectady, county of Schenectady, State of New York, have invented certain new and useful Improvements in Rheostats, (Case No. 1334,) of which the following is a specification.

This invention relates to rheostats, the 0bject being to provide adevice of this character strong and simple in construction and having large heat-dissipating capacity.

In carrying out the invention I form the resistance material of wire, crimped into zig- Zag form and firmly supported between metal plates, the contact-faces of which are coated with enamel or similar tenacious insulating refractory material, loops of the resistancewire being permitted to project from the sup porting-plates for connection with a range of studs or contacts by which the length of resistance-wire in circuit may be varied. The wire is first passed through a crimpingma chine and is then folded back and forth upon itself in annular or other form with intervening air-spaces and submitted to heat and pressure between metallic plates in order to prevent it springing and is then placed between the enameled plates and connected with the studs on the rheostats.

The several features of novelty of the invention will be hereinafter more fully described and will be definitely indicated in the claims accompanying this specification.

In the drawings, Figure l is a sectional detail of a rheostat embodying my improven ments, and Fig. 2 is a partial plan View of a rheostat with parts broken away.

l represents a metallic wire, which may be of any metal suitable for resistance-boxes or rheostats, crimped by preliminary treatment in a, crimping-machine and then folded back and forth in zigzag form in annular or other shape and pressed and heated between metal plates. It is then clamped between metal plates 2 3, the opposing faces of which are covered with an insulating-enamel,the plates being held together by bolts or set-screws t 4.a. The wire, of course, may be arranged in other form than that shown, the essential feature being that the main part of it is firmly held Serial No. 56,817. (No model.)

between plates which conduct away and dis:

sipate the heat generated in the wire. outer ends of the folds are permitted to project beyond the plates, as indicated at 5, and are held between metal washers 6 6, screwed firmly on a pin 7, passing through an annulus of porcelain S, the upper ends of the pin being headed to form contactstuds 9 9, due. The number of extended loops of the resistance-wire may be varied according to the fineness of resistance graduation in the several steps. As shown in the drawings, each loop is taken out to a separate resistance-stud, though of course everysecond, third, or fourth loop may be taken out, if desired.

The ends of the wire may be connected in any usual manner with respect to the circuit, one terminal of which may be placed on an insulated post for the operating-handle, if desired; but I prefer to mount a conductingring lO on the porcelain ring 8 and employ a bridging contact 1l, carried by and insulated from a spring-arm 12, attached to the operating-handle 13.

The plates 2 3 may be formed so as to constitute the frame of the rheostat, as will be evident from the drawings, the plate 2 being a disk dished at the center and plate 3 an annulus dished at the circumference and provided with lugs la 14n to form feet for the rheostat. The loops of resistance-wire projecting from beneath the plates are thus suspended in an air-space, across which extends the porcelain ring 8, thus permitting free ventilation and facilitating cooling of the wire, while the surface of the metal plates 2 3 is in open exposure to the air and rapidly carries away the heat of the wire.

What I claim as new, and desire to secure by Letters Patent of the United States, is-u 1. A rheostat having a length of resistancewire bent back and forth upon itself, and mounted between insulated heat-conducting plates, a number of bends of the wire being permitted to project from the edges of the plates, and contact-studs connected with said bends.

2. A rheostat having a plurality of folds of resistance material clamped between met-al plates coated with insulating heat-refractory material, a number of folds projecting from The IOO

the edges of the plates and connected with contact-studs.

3. A rheostat having a resistance in zigzag form and clamped between insulated metal plates having projecting loops intermediate the ends for effecting contact.

4. A rheostat comprising a crimped resistance-wire clamped between insulated metal plates, a range of insulated contact-stu ds connecting with different parts of resistance-wire, a conductor arranged adjacent to, but insulated from said studs and a bridging contact to connect the two.

5. A rheostat comprising a folded wire clamped between enameled metal plates, a ring of insulating material carrying a range of contact-studs connecting with successive parts of resistance-wire, a metal ring mounted on the insulating-ring adjacent to the studs and forming one terminal of the circuit, and a bridging contact secured to an operatinghandle to connect the several studs with the metal ring.

G. A rheostat comprisingr a crimped resistance-wire folded in zigzag form and clamped between enameled metal plates, loops of the wire projecting `from the plates atintervals and surrounded by an air-space, a porcelain ring carrying contact-studs connected with the projecting loops and a movable switch adapted to sweep over the contact-studs.

7. A rheostat having a continuous integral length of conductor clamped between insulated metal plates and having integral loops extending from the plates and contact-studs connecting with said loops.

In witness whereof I have hereunto set my hand this 20th day of April, 1901.

FREDERICK MACKINTOSH.

Witnesses:

BENJAMIN B. HULL, MARGARET E. WooLLEY. 

